Ceramic structural body

ABSTRACT

Ceramic structural body having improved material properties of a sealing member, such as adhesion properties at room temperature and high temperature, and having an improved durability. The ceramic structural body comprises an assembly of plural united ceramic members each having a plurality of through-holes arranged side by side along a longitudinal direction, in which end faces at either side of these through-holes are closed in a checkered pattern so as to have a reverse relation of open and close between gas inlet side and gas outlet side and adjacent through-holes are permeable to each other through porous partition walls. A plurality of the ceramic members are integrally adhered by interposing a sealing member of an elastic material comprising at least inorganic fibers, an inorganic binder, an organic binder and inorganic particles and mutually bonded three-dimensionally intersected organic fibers and inorganic particles through the inorganic binder and organic binder between the mutual ceramic members.

TECHNICAL FIELD

This invention relates to a ceramic structural body, and moreparticularly it proposes an improvement in the structure of the ceramicstructural body made by piercing a plurality of through-holes inparallel to each other along a longitudinal direction of a member, suchas a ceramic honeycomb structural body, monolithic structural body andthe like.

DISCUSSION OF BACKGROUND INFORMATION

In general, the ceramic structural body such as a ceramic honeycombstructural body and the like formed by piercing a plurality ofthrough-holes in the longitudinal direction of the member in parallel toeach other is used as a filter for purifying exhaust gas discharged fromvehicles, factories and the like.

This ceramic structural body has such an end face that the open-closecondition of the through-holes shows a checkered pattern (the state thatadjacent through-holes are alternately in the open-close condition).That is, these through-holes are sealed at either only one of their endfaces, and adjacent through-holes are opened or closed from each otherto form the checkered pattern. Therefore, when one through-hole isopened at one end face, the other end face is sealed, while the adjacentthrough-hole thereto is sealed at one end face and opened at the otherend face.

Moreover, the ceramic structural body is such a porous body that when agas to be treated is flown from either one end face of each of the abovethrough-holes, the treated gas enters into an adjacent through-holepassing through porous partition walls on the way toward the other endface and then discharges out from such other end face. That is, theceramic structural body is made possible to mutually pass the gasthrough the partition wall separating the through-holes. Therefore, thegas to be treated easily passes into the other through-hole in thestructural body, so that the gas passes through different through-holesat the inlet side and outlet side.

Therefore, when the exhaust gas is passed through the above ceramicstructural body, particle substances (particulate) in the exhaust gasare caught and purified in the partition wall portion while passing theexhaust gas flown from one-side end face through the partition walltoward the outlet port. With the purifying action of the exhaust gas,the ceramic structural body degrades the pass of the gas because theparticulate is collected and accumulated in the partition wall at theinlet port side to gradually create clogging. Therefore, the ceramicstructural body requires a treatment for periodically burning andremoving the particulate accumulated on the partition wall, whichresults in the clogging, by a heating mechanism such as burner, heateror the like (hereinafter simply referred to as "regeneration").

The above ceramic structural body, however, causes nonuniformtemperature distribution inside the structural body due to local heatgeneration accompanied with nonuniform heating process and abnormalburning of particulate, thermal shock given by sudden temperature changeof exhaust gas and the like so as to bring about the action of thermalstress. As a result, the above ceramic structural body has encounteredsuch problems that crack generation and hence molten loss are invitedand finally led to breakage so as to impede collection of particulate.

On the contrary, hitherto, as means for solving the above problems,there has been proposed, for example, a method for decreasing thermalstress acting on a ceramic structural body by dividing the ceramicstructural body into a plurality of ceramic members on the faceperpendicular to the axis or the face in parallel with the axis (seeJP-A-60-65219). Moreover, there has been proposed a divided ceramicstructural body having improved property for sealing the exhaust gas byinserting a non-adhesion sealing member in a gap produced between themutual ceramic members in this divided-type ceramic structural body(hereinafter referred to as "divided ceramic structural body") (seeJU-A-1-63715).

According to the above respective proposals, the divided ceramicstructural body can liberate thermal stress observed in a one-piececeramic structural body owing to the use of the above sealing member.

However, the sealing member is non-adhesive, so that the ceramic memberscannot be firmly joined to each other. Therefore, the above dividedceramic structure body according to the conventional technique wasrequired to have a restraint force for uniting these ceramic members tomaintain the form of a one-piece structural body. Therefore, as meansfor giving this restraint force, there has hitherto been used anarrangement of a thermally expansive heat insulator or an application ofthe thermally expansive heat insulator as an inner sealing member.

However, the above non-adhesion sealing member and the thermallyexpansive heat insulator are poor in the durability to heat in theregeneration and repetition of oscillation generated from aninternal-combustion engine. Therefore, the sealing member proceeds thedegradation of volume shrinkage and strength to lower the sealingproperty, while the thermally expansive heat insulator has a problem torapidly lower the restoring force after volume expansion.

Therefore, the above divided ceramic structural body has lost force forsupporting a plurality of ceramic members constituting this structuralbody, and decomposed and dispersed by the pressure of the exhaust gas.Moreover, even if a reinforcing member is arranged at an end face at anoutlet side of the gas, it is difficult to prevent the degradation ofthe sealing member, and it is desired to improve the durability.

Particularly, in order to form a large-size divided ceramic structuralbody, a larger restraint force is required, the combination of theconventional non-adhesion sealing member and thermally expansive heatinsulator cannot deal with from the beginning, so that a structural bodyis not obtained that can withstand stress to be practically useful.

Under the above circumstances, the inventors have previously proposed"EXHAUST GAS PURIFYING APPARATUS AND STRUCTURAL BODY THEREOF" with theuse of a sealing member consisting of ceramic fiber, silicon carbidepowder and inorganic binder by improving the sealing member constitutingthe divided ceramic structural body as means for overcoming the problemsinherent to the above conventional technique (see Japanese PatentApplication No. 5-204242).

According to this proposal, a plurality of ceramic members are joined toeach other through such a sealing member, so that it is possible toimprove the durability of the divided ceramic structural body to acertain extent.

However, the sealing member tends to easily cause migration (phenomenonof moving a binder with drying and removal of a solvent) when it isfilled and cured between the mutual ceramic members. Therefore, the seallayer formed by curing the sealing member becomes brittle.

That is, the inorganic binder constituting the above sealing member actsto firmly join the ceramic member to the seal layer and to join anintersect point of three-dimensionally crossed ceramic fibers as animportant element for developing stress buffering function of the seallayer. However, the inorganic binder moves from the inside of the seallayer to the joint face with the ceramic member through the migrationproduced in the course of drying and curing, whereby the joint force atthe intersect point is decreased, and hence the strength of the ceramicstructural body itself is lowered, so that the desired durability couldnot be satisfied.

Furthermore, the silicon carbide powder constituting the sealing memberalso moves with the above migration to bring about the lowering andnonuniformity of thermal conductivity, which results in the lowering ofthe regeneration efficiency of the ceramic structural body.

On the contrary, there is considered a method of improving thedurability of the structural body by controlling the migration. However,this method takes a long time for drying and curing the sealing memberant undesirably degrades the productivity.

As mentioned above, the conventional divided ceramic structural bodystill leaves room for improvement with respect to durability and thelike as a ceramic structural body.

SUMMARY OF THE INVENTION

The invention is made for solving the above-described various problemsinherent to the conventional technique, and its main object is toimprove the durability of the ceramic structural body.

Another object of the invention is to improve material properties suchas adhesion properties of a sealing member at room temperature and hightemperature and the like.

The other object of the invention is to improve the adhesion propertyand thermal conductivity of the sealing member at room temperature andhigh temperature while maintaining elasticity and heat resistance tothereby simultaneously improve both durability and regenerationefficiency of the divided ceramic structural body.

The inventors have made further studies to realize the above objects. Asa result, the inventors have found an invention having the constructionmentioned below.

That is, the invention lies in a ceramic structural body comprising anassembly of plural united ceramic members each having a plurality ofthrough-holes arranged side by side along a longitudinal direction, inwhich end faces at either side of these through-holes are closed in acheckered pattern so as to have a reverse relation of open and closebetween gas inlet side and gas outlet side and adjacent through-holesare permeable to each other through porous partition walls,characterized in that a plurality of the ceramic members are integrallyadhered by interposing a sealing member of an elastic materialconsisting of at least inorganic fibers, an inorganic binder, an organicbinder and inorganic particles and mutually bonded three-dimensionallyintersected organic fibers and inorganic particles through the inorganicbinder and organic binder between the mutual ceramic members.

The sealing member is desirable to be an elastic material formed byusing ceramic fiber as the inorganic fiber, using colloidal sol as theinorganic binder, using polysaccharide as the organic binder, and usingat lease one inorganic powder or whisker selected from carbides andnitrides as the inorganic particle, and mixing them each other.Particularly, the sealing member is desirable to be an elastic materialformed by using at least one ceramic fiber selected from silica-alumina,mullite, alumina and silica as the inorganic fiber, using at least onecolloidal sol selected from silica sol and alumina sol as the inorganicbinder, using at least one polysaccharide selected from polyvinylalcohol, methyl cellulose, ethyl cellulose and carboxymethyl celluloseas the organic binder and using at least one inorganic powder or whiskerselected from silicon carbide, silicon nitride and boron nitride as theinorganic particle. More particularly, it is desirable to be an elasticmaterial consisting of silica-alumina ceramic fiber, silica sol,carboxymethyl cellulose and silicon carbide powder.

Concretely, the above sealing member is favorable to have the followingcomposition.

1 In the ceramic fiber, it is desirable that the content ofsilica-alumina fiber is 10˜70 wt %, preferably 10˜40 wt %, morepreferably 20˜30 wt % as a solid content. Because, when the content isless than 10 wt %, the effect as an elastic body lowers, while when itexceeds 70 wt %, the thermal conductivity lowers and also the effect asan elastic body lowers.

2 In the colloidal sol, it is desirable that the content of silica solis 1˜30 wt %, preferably 1˜15 wt %, more preferably 5˜9 wt % as a solidcontent. Because, when the content is less than 1 wt %, the adhesionstrength lowers, while when it exceeds 30 wt %, the thermal conductivitylowers.

3 In the polysaccharide, it is desirable that the content ofcarboxymethyl cellulose is 0.1˜5.0 wt %, preferably 0.2˜1.0 wt %, morepreferably 0.4˜0.6 wt % as a solid content. Because, when the content isless than 0.1 wt %, migration cannot be controlled, while when itexceeds 5.0 wt %, the organic binder is burnt out by thermal hysteresisof high temperature, and the strength lowers.

4 In the inorganic powder or whisker, it is desirable that the contentof silicon carbide powder is 3˜80 wt %, preferably 10˜60 wt %, morepreferably 20˜40 wt % as a solid content. Because, when the content isless than 3 wt %, the thermal conductivity lowers, while when it exceeds80 wt %, the adhesion strength at high temperature lowers.

5 In the ceramic fiber constituting the sealing member, thesilica-alumina ceramic fiber is desirable to have a shot content of 1˜10wt %, preferably 1˜5 wt %, more preferably 1˜3 wt %, and a fiber lengthof 0.1˜100 mm, preferably 0.1˜50 mm, more preferably 0.1˜20 mm. Because,when the shot content is less than 1 wt %, the production is difficult,while when the shot content exceeds 10 wt %, a wall of a member to besealed (ceramic member) is damaged. On the other hand, when the fiberlength is less than 0.1 mm, an elastic structural body can not beformed, while when it exceeds 100 mm, the fiber becomes fluffy to makedispersion of the inorganic particles worse, and also the thickness ofthe sealing member cannot be made thin to bring about the lowering ofthermal conductivity between the members to be sealed.

6 In the inorganic powder or whisker constituting the sealing member, itis desirable that the particle size of the silicon carbide powder is0.01˜100 μm, preferably 0.1˜15 μm, more preferably 0.1˜10 μm. Because,when the particle size exceeds 100 μm, the adhesion force (strength) andthermal conductivity lower, while when it is less than 0.01 μm, the costbecomes undesirably high.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a filter for an exhaust gaspurifying apparatus with the use of the ceramic structure body accordingto the invention. FIG. 2 is a partially enlarged sectional view of thefilter for the exhaust gas purifying apparatus with the use of theceramic structure body according to the invention. FIG. 3 is aperspective view of a ceramic member in the filter for the exhaust gaspurifying apparatus according to the invention. FIG. 4 is a partiallycutaway enlarged sectional view taken along line A--A of FIG. 3. FIG. 5is an enlarged sectional view taken along line B--B of FIG. 4. FIG. 6 isa view illustrating a test for the measurement of adhesion strength.FIG. 7 is a view illustrating a test for the measurement of thermalconductivity.

Reference numeral 1 is a filter for an exhaust gas purifying apparatus,numerals 2 and 3 ceramic members, numeral 4 a sealing member, andnumeral 5 a heat insulator.

BEST MODE FOR CARRYING OUT THE INVENTION

An essential feature of the ceramic structural body according to theinvention lies in a construction of a sealing member capable ofintegrally uniting a plurality of ceramic members.

Concretely, there is a first point of improving the durability of theceramic structural body by entangling the inorganic fibers and organicbinder constituting the sealing member with each other to improve theuniformity of the structure and the joining property at a lowtemperature region. That is, it is an essential point that it ispossible to maintain the three-dimensional bond of inorganic fibers andfixation of inorganic particles to inorganic fibers by adopting anorganic binder capable of drying and curing at an early stage to controlthe occurrence of migration as seen in the conventional sealing member.

Thus, the sealing member may be an elastic material having a uniformstructure and excellent adhesion property, elasticity and strength. As aresult, the ceramic structural body formed by integrally uniting aplurality of ceramic members with such sealing members has a sufficientadhesion strength without giving any restraint force from an externalrestraining member and can simultaneously liberate thermal stress.

A second point lies in that the adhesion strength at a high temperatureregion can be maintained by the entangling effect of the inorganicfibers and the inorganic binder constructing the sealing member. Thereason is considered due to the fact that the organic binder is calcinedand removed at the high temperature region, but the inorganic binder isrendered into ceramic by heating, and this ceramic exists in intersectpoints of the inorganic fibers and contributes to joining between theinorganic fibers and between the inorganic fiber and the ceramic member.On the other hand, the inorganic binder can hold the adhesion strengtheven at the low temperature region through drying and heating.

Therefore, the ceramic structural body having excellent adhesionstrengths at low temperature region and high temperature region can beformed by a synergistic action of the organic binder with the aboveeffect of entangling the ceramic fibers such as silica-alumina with theinorganic binder such as silica sol.

A third point lies in that the inorganic particles are existent on thesurface of the inorganic fiber and the surface of the inorganic binderor the inside thereof to improve the thermal conductivity of the ceramicstructural body.

Particularly, inorganic particles such as nitride and carbide, canconsiderably improve the thermal conductivity owing to a high thermalconductivity property inherent to the nitride and carbide.

Therefore, the sealing member containing the inorganic particles hasexcellent thermal conductivity and can effectively prevent the breakageof the ceramic structural body without causing temperature peakphenomenon at the regeneration while filling gaps produced in thecombination of plural ceramic members when the sealing member is used,for example, as a filter for an exhaust gas purifying apparatus.Moreover, the occurrence of cracks by heat cycle can be reduced, and theedge portion of the outer periphery of the filter can be heated in arelatively short time to improve the regeneration efficiency.

The ceramic structural body according to the invention will be describedin detail as follows.

When the ceramic structural body is used as a filter for an exhaust gaspurifying apparatus, the sealing member constituting the structural bodyis necessary to have elasticity, thermal conductivity, joining property,strength and the like in addition to heat resistance. When theelasticity is excellent, even if thermal stress is applied to the filterby heating, this thermal stress can surely be liberated. Further, whenthe thermal conductivity is excellent, heat of a heating element isimmediately and evenly conducted to the whole of the structural body,and the temperature difference in the exhaust gas purifying apparatus isminimized. Moreover, when the joining property and strength areexcellent, the adhesion property between the adjacent united ceramicmembers becomes excellent, and the durability of the ceramic structuralbody itself becomes excellent.

The invention lies in that the construction of the sealing memberexhibiting the above properties is an elastic structural body formed byusing the inorganic fibers, inorganic binder, organic binder andinorganic particles and mutually bonding the three-dimensionallyintersected inorganic fibers and inorganic particles through theinorganic binder and organic binder.

As the inorganic fiber, there are silica-alumina ceramic fiber, mullitefiber, alumina fiber and silica fiber. Particularly, the silica-aluminaceramic fiber is desirable because it is excellent in the elasticity andshows a function of absorbing thermal stress.

As the inorganic binder, colloidal sol is desirable, which includes, forexample, alumina sol and silica sol. Particularly, silica sol isdesirable, which acts as an adhesive (inorganic binder). This silica solis easily available and suitable as an adhesive at high temperatureregion because it is easily changed into SiO₂ by firing, and isexcellent in the insulating property.

As the organic binder, a hydrophilic organic high polymer is desirable,and particularly polysaccharide is more preferable. Concretely, thereare polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethylcellulose and the like. Among them, carboxymethyl cellulose isparticularly desirable because it secures the fluidity at the time ofassembling (contributes to improvement of workability) and shows anexcellent adhesion property at room temperature region.

As the inorganic particle, inorganic particles of carbide and/or nitrideare desirable, such as silicon carbide, silicon nitride and boronnitride. These carbide and nitride are very large in the thermalconductivity and contribute to the improvement of the thermalconductivity by existing on the surface of ceramic fiber and the surfaceand inside of colloidal sol. For example, the thermal conductivity ofsilicon carbide is 0.19 cal/cm•sec•°C., and the thermal conductivity ofboron nitride is 0.136 cal/cm•sec•°C., while the thermal conductivity ofalumina is about 0.08 cal/cm•sec•°C., so that it is understood that thecarbide and nitride are particularly effective for improving the thermalconductivity.

Among the inorganic particles of these carbide and nitride, siliconcarbide is particularly optimum in view of the thermal conductivity.Boron nitride is lower than silicon carbide in the affinity with ceramicfiber. That is, silicon carbide possesses all of adhesion property, heatresistance, water resistance and thermal conductivity.

An embodiment of using the ceramic structural body according to theinvention in a filter for an exhaust gas purifying apparatus attached toa diesel engine will be described in detail with reference to FIGS. 1˜5below.

FIG. 1 shows a filter 1 for an exhaust gas purifying apparatus using theceramic structural body according to the invention, and FIG. 2 is apartially enlarged section view of the filter. In these figures, thefilter 1 for the exhaust gas purifying apparatus is constructed byintegrally adhering eight prismatic ceramic members 2 and four ceramicmembers 3 of a right angle equilaterally triangle in section throughsealing members 4 (1.5˜3.0 mm in thickness) of an elastic materialinterposed between the mutual members.

FIGS. 3˜5 show the ceramic member 2 constituting a part of the filterfor the exhaust gas purifying apparatus. In these figures, through-holes2a of an approximately square shape in section are regularly pierced inthe ceramic member 2 of a prismatic shape (33 mm×33 mm×150 mm) along itsaxial direction. These through-holes 2a are separated from each otherwith porous partition walls 2b of 0.3 mm in thickness. Either one end ofexhaust gas inlet side and outlet side of each of the through-holes 2ais sealed with a sealing piece 2c of a porous sintered body in acheckered pattern. As a result, cells C1, C2 are formed so as to openonly to either one of the inlet side and outlet side of the ceramicmember 2. Moreover, an oxidation catalyst comprised of platinum element,other metal element or an oxide thereof may be carried on the partitionwalls 2b of the cells C1, C2 because an ignition temperature of theparticulate lowers by the carrying. Moreover, the ceramic member 3 hasthe same construction as the ceramic member 2 except that the crosssection is right angle equilateral triangle. In case of the ceramicmembers 2, 3 constituting the filter 1 for the exhaust gas purifyingapparatus of this embodiment, there are set a mean pore diameter to 10μm, a porosity to 43%, a thickness of a cell wall to 0.3 mm, and a cellpitch to 1.8 mm, respectively.

In this embodiment, the filter 1 for the exhaust gas purifying apparatushaving the aforementioned structure is prepared to conduct theevaluation of performances in the filter.

EXAMPLE 1

(1) 51.5 wt % of α-type silicon carbide powder and 22 wt % of β-typesilicon carbide powder were wet mixed, and the resulting mixture wasadded and kneaded with 6.5 wt % of an organic binder (methyl cellulose)and 20 wt % of water. Next, small amounts of a plasticizer and alubricant were added and kneaded, which was extrusion-molded to obtain ahoneycomb green shaped body.

(2) Next, this green shaped body was dried by using a microwave drier.Thereafter, through-holes 2a of the shaped body were sealed with a pastefor the formation of a sealing piece 2c made of a porous sintered body,and then the paste for the sealing piece 2c was dried by using the drieragain. After the dried body was degreased at 400° C., it was furtherfired in an argon atmosphere at 2200° C. to obtain porous honeycombceramic members 2, 3.

(3) A sealing member was prepared from a paste obtained by mixing andkneading 23.3 wt % of ceramic fiber (alumina silicate ceramic fiber,shot content: 3 wt %, fiber length: 0.1˜100 mm), 30.2 wt % of siliconcarbide powder of 0.3 μm in mean particle size, 7 wt % of silica sol(SiO₂ conversion amount of sol: 30%) as an inorganic binder, 0.5 wt % ofcarboxymethyl cellulose as an organic binder and 39 wt % of water.

(4) The above sealing member was filled between the mutual ceramicmembers 2, 3, dried and cured at 50˜100° C.×1 hour to prepare a filter 1integrally joining the ceramic members 2, 3 with the sealing member 4 asshown in FIG. 1.

Moreover, the above sealing member could be dried and cured withoutcausing migration.

EXAMPLE 2

This example is fundamentally the same as Example 1, but the followingsealing member was used instead of that of Example 1.

It was used by mixing and kneading 25 wt % of ceramic fiber (mullitefiber, shot content: 5 wt %, fiber length: 0.1˜100 mm), 30 wt % ofsilicon nitride powder of 1.0 μm in mean particle size, 7 wt % ofalumina sol (conversion amount of alumina sol: 20%) as an inorganicbinder, 0.5 wt % of polyvinyl alcohol as an organic binder and 37.5 wt %of alcohol.

Moreover, the above sealing member could be dried and cured withoutcausing migration.

EXAMPLE 3

This example is fundamentally the same as Example 1, but the followingsealing member was used instead of that of Example 1.

It was used by mixing and kneading 23 wt % of ceramic fiber (aluminafiber, shot content: 4 wt %, fiber length: 0.1˜100 mm), 35 wt % of boronnitride powder of 1 μm in mean particle size, 8 wt % of alumina sol(conversion amount of alumina sol: 20%) as an inorganic binder 0.5 wt %of ethyl cellulose as an organic binder and 35.5 wt % of acetone.

Moreover, the above sealing member could be dried and cured withoutcausing migration.

Comparative Example

This example is fundamentally the same as Example 1, but the followingconventional sealing member was used instead of the sealing member inExample 1 and further an outermost peripheral portion of the filter 1was covered with a heat insulator (63 wt % of ceramic fiber, 7 wt % ofα-sepiolite, 20 wt % of unexpanded vermiculite and 10 wt % of an organicbinder).

It was used in form of paste or sheet by mixing and kneading 44.2 wt %of ceramic fiber (alumina-silica fiber, shot content: 2.7 wt %, fiberlength: 30˜100 mm), 13.3 wt % of silica sol as an inorganic binder and42.5 wt % of water.

Moreover, the above sealing member caused migration at the time ofdrying and curing.

The evaluation of performances with respect to the filters 1 prepared inExamples 1˜3 and Comparative Example was carried out by the followingmethod.

Measurement of adhesion strength at initial stage and after heat cycle!

As shown in FIG. 6, a test piece corresponding to three ceramic memberswas cut from the filter 1 and a load was applied to a central ceramicmember to measure a load causing the peeling. Moreover, since quickheating and quenching from room temperature to 900° C. were anticipatedin actual use, the test piece was subjected to a heat cycle test of roomtemperature ˜900° C.

Table 1 shows results measured on the adhesion strength at an initialstage and after heat cycle (after 100 cycles) between the mutual ceramicmembers 2, 3 constituting the filter 1. Moreover, the reason why thestrength after heat cycle is improved is assumed due to the sinteringaction of silica by heating at 900° C.

                  TABLE 1    ______________________________________               Adhesion strength                         Adhesion strength               at initial stage                         after heat cycle    ______________________________________    Example 1    4.6 kg/cm.sup.2                             7.6 kg/cm.sup.2    Example 2    4.5 kg/cm.sup.2                             5.3 kg/cm.sup.2    Example 3    4.3 kg/cm.sup.2                             5.6 kg/cm.sup.2    Comparative  2.3 kg/cm.sup.2                             0.76 kg/cm.sup.2    Example 1    ______________________________________

Measurement of thermal conductivity!

As shown in FIG. 7, a test piece corresponding to four ceramic memberswas cut out and covered on its outer periphery with a heat insulator andplaced on a heater 6 to conduct heating for 20 minutes. A temperaturedifference between T1 and T2 was measured.

Table 2 shows results measured on the temperature difference between T1and T2 shown in FIG. 7 with respect to Examples 1˜3 and ComparativeExample.

                  TABLE 2    ______________________________________              T1 - T2 temperature difference    ______________________________________    Example 1   55° C.    Example 2   65° C.    Example 3   70° C.    Comparative 180° C.    Example    ______________________________________

As seen from the above results, the filter using the ceramic structuralbody according to the invention has considerably high adhesion strengtheven at both high temperature and room temperature, and is excellent inthe heat cycle property, so that it was confirmed that the durability asa filter is excellent.

And also, this ceramic structural body is excellent in the thermalconductivity, so that the occurrence of peak temperature in the ceramicmember located inside the filter can be reduced and also the temperaturerising time of the ceramic structural body located at the edge portioncan be shortened and hence the improvement of the regenerationefficiency can simultaneously be realized.

Moreover, the construction of the filter 1 applying the ceramicstructural body according to the invention is not limited to thosedescribed in the above examples, and can be changed to the followingconstruction. For example,

(a) The number of combined ceramic members is not necessarily 12 as inthe examples, but any optional number is possible. In this case, it isnaturally possible to properly combine ceramic members having differentsizes, forms and the like. Moreover, the adoption of the constructionmade by combining plural ceramic members is particularly advantageous inthe manufacture of a filter for a large-sized exhaust gas purifyingapparatus. purifying apparatus.

(b) The filter 1 of the above examples can be grasped to be at a stateof dividing the so-called one large filter into the plural parts alongthe axial direction. Therefore, there are considered, for example, thestate of dividing the filter into a doughnut, the state of dividing thefilter in a direction perpendicular to the axial direction and the like.

(c) It is naturally possible to adopt not only the honeycomb-shapedceramic members 2, 3 as shown in the above examples but alsothree-dimensional network structure, foam structure, noodle structure,fiber structure and the like. Moreover, the material for the ceramicmembers 2, 3 may naturally be selected from any other than siliconcarbide.

(d) In case of constructing the filter 1, a heater may be arrangedbetween the ceramic members 2, 3. In this case, the heater is notlimited to be a metallic wire. That is, the heater may be prepared by amethod such as metal metallizing, printing of conductor paste,sputtering or the like.

Although the above examples are described with respect to the case ofapplying the ceramic structural body according to the invention to thefilter for an exhaust gas purifying apparatus attached to the dieselengine, this ceramic structural body can be used, for example, as a heatexchanger member or a filter for filtering high temperature fluid orhigh temperature vapor in addition to the filter for the exhaust gaspurifying apparatus.

INDUSTRIAL APPLICABILITY

As mentioned above, the ceramic structural body according to theinvention is excellent in the adhesion strength regardless oftemperature, and further excellent in the thermal conductivity, so thatif it is applied to a filter for an exhaust gas purifying apparatus, itis possible to realize the shortening of regeneration time and theimprovement of regeneration efficiency and durability.

We claim:
 1. A ceramic structural body comprising:an assembly of aplurality of ceramic members; each of said plurality of ceramic memberscomprising:a plurality of through-holes arranged side-by-side along alongitudinal direction between opposing end faces comprising a gas inletside and a gas outlet side; through-holes in said opposing end face onsaid gas inlet side being closed in a checkered pattern andthrough-holes in said opposing end face on said gas outlet side beingclosed in a reverse relation so that through-holes that are open on saidgas inlet side are closed on said gas outlet side; and adjacentthrough-holes being permeable to each other through porous partitionwalls; and sealing member integrally adhering said plurality of ceramicmembers, said sealing member being interposed between adjacent ceramicmembers, and being composed of an elastic material comprising inorganicfibers, inorganic binder, organic binder and inorganic particles.
 2. Theceramic structural body according to claim 1, wherein said inorganicfibers comprise ceramic fibers, said inorganic binder comprisescolloidal sol, said organic binder comprises polysaccharide, and saidinorganic particles comprise at least one member selected from the groupconsisting of carbide and nitride inorganic powders or whiskers.
 3. Theceramic structural body according to claim 2, wherein said ceramicfibers are at least one member selected from the group consisting ofsilica-alumina, mullite, alumina and silica.
 4. The ceramic structuralbody according to claim 2, wherein said colloidal sol is at least onemember selected from the group consisting of silica sol and alumina sol.5. The ceramic structural body according to claim 2, wherein saidpolysaccharide is at least one member selected from the group consistingof polyvinyl alcohol, methyl cellulose, ethyl cellulose andcarboxymethyl cellulose.
 6. The ceramic structural body according toclaim 2, wherein said at least one member selected from the groupconsisting of carbide and nitride inorganic powders or whiskers is atleast one member selected from the group consisting of silicon carbide,silicon nitride and boron nitride.
 7. The ceramic structural bodyaccording to claim 2, wherein said sealing member comprisessilica-alumina ceramic fiber, silica sol, carboxymethyl cellulose andsilicon carbide powder.
 8. The ceramic structural body according toclaim 7, wherein said sealing member comprises about 10 to 70 wt % ofsilica-alumina ceramic fiber, about 1 to 30 wt % silica sol, about 0.1to 5.0 wt % carboxymethyl cellulose, and about 3 to 80 wt %, based upontotal solid weight.
 9. The ceramic structural body according to claim 7,wherein said silica-alumina ceramic fiber has a shot content of about 1to 10 wt % and a fiber length of about 1 to 100 mm.
 10. The ceramicstructural body according to claim 7, wherein the silicon carbide powderhas a particle size of about 0.01 to 100 μm.
 11. A ceramic structuralbody comprising:an assembly of a plurality of ceramic members; each ofsaid plurality of ceramic members comprising:a plurality ofthrough-holes arranged side-by-side along a longitudinal directionbetween opposing end faces comprising a gas inlet side and a gas outletside; through-holes in said opposing end face on said gas inlet sidebeing closed in a checkered pattern and through-holes in said opposingend face on said gas outlet side being closed in a reverse relation sothat through-holes that are open on said gas inlet side are closed onsaid gas outlet side; and adjacent through-holes being permeable to eachother through porous partition walls; and sealing member integrallyadhering said plurality of ceramic members, said sealing member beinginterposed between adjacent ceramic members, and being composed of anelastic material comprising inorganic fibers, inorganic binder, organicbinder and inorganic particles, and said organic binder and inorganicbinder bonding said inorganic particles to said inorganic fibers. 12.The ceramic structural body according to claim 11, wherein saidinorganic fibers comprise ceramic fibers, said inorganic bindercomprises colloidal sol, said organic binder comprises polysaccharide,and said inorganic particles comprise at least one member selected fromthe group consisting of carbide and nitride inorganic powders orwhiskers.
 13. The ceramic structural body according to claim 11, whereinsaid ceramic fibers comprise at least one member selected from the groupconsisting of silica-alumina, mullite, alumina and silica.
 14. Theceramic structural body according to claim 11, wherein said colloidalsol is at least one member selected from the group consisting of silicasol and alumina sol.
 15. The ceramic structural body according to claim11, wherein said polysaccharide is at least one member selected from thegroup consisting of polyvinyl alcohol, methyl cellulose, ethyl celluloseand carboxymethyl cellulose.
 16. The ceramic structural body accordingto claim 12, wherein said at least one member selected from the groupconsisting of carbide and nitride inorganic powders or whiskers is atleast one member selected from the group consisting of silicon carbide,silicon nitride and boron nitride.
 17. The ceramic structural bodyaccording to claim 12, wherein said sealing member comprisessilica-alumina ceramic fiber, silica sol, carboxymethyl cellulose andsilicon carbide powder.
 18. The ceramic structural body according toclaim 17, wherein said sealing member comprises about 10 to 70 wt % ofsilica-alumina ceramic fiber, about 1 to 30 wt % silica sol, about 0.1to 5.0 wt % carboxymethyl cellulose, and about 3 to 80 wt %, based upontotal solid weight.
 19. The ceramic structural body according to claim17, wherein said silica-alumina ceramic fiber has a shot content ofabout 1 to 10 wt % and a fiber length of about 1 to 100 mm.
 20. Theceramic structural body according to claim 17, wherein the siliconcarbide powder has a particle size of about 0.01 to 100 μm.